The biggest question in Maryland politics is: Will former Gov. Bob Ehrlich seek a rematch with Gov. Martin O'Malley? As Ehrlich decides, a survey of the political landscape reveals that much has changed since he became the state's first Republican governor in 36 years. Some of that was already evident in 2006 when he was defeated, but as he ponders his future, Ehrlich has cause for concern and optimism. Should he run, the road to Annapolis would be steep and the journey influenced as much by national trends as by issues specific to Maryland.

Good and bad news

As of October, Maryland had 1,940,634 Democrats and 906,679 Republicans, a 56.8 percent to 26.6 percent advantage. The 2-to-1 advantage should give Ehrlich pause, and the trend should cause nightmares. Since 2002 Democrats have added 384,000 voters while Republicans have added 73,000. Given that Ehrlich won by 67,000 votes in 2002 and lost by nearly 117,000 in 2006, he must question how he could overcome the Democrats' advantage.

Ehrlich won nearly 52 percent of the vote in 2002, though Democrats enjoyed a 56 percent to 30 percent registration advantage. In 2006 he received 46 percent, though Republicans were but 28.9 percent of registered voters. The Republicans' disadvantage does not correlate to final vote totals. In all but one of the last four gubernatorial elections, the Democratic candidate underperformed relative to the registration advantage and in all four, the Republican candidates exceeded their partisan share of the electorate. Simply put, many registered Democrats and unaffiliated and third party voters vote Republican.

Though Democrats won three of the last four gubernatorial elections, the 1994 and 2002 results show that Republicans can win. In 1994, the Democrat won by a scant 5,993 votes. In 2002, Ehrlich won. In 1994 and 2002 the Democrat received a total statewide vote equal to 80.5 percent and 83 percent respectively of the total Democrats voting and the GOP candidate over-performed by 155.6 percent and 156.5 percent. Democrats won in 1998 and 2006 because their candidate performed on par with their partisan share of the electorate and the GOP candidate failed to sufficiently over-perform.

That Republicans did so well in 1994 and 2002 matters, as both were good years for the GOP nationally. In 1994 Republicans won control of the House and the Senate; in 2002 they gained seats. In contrast, 1998 and 2006 were good years for Democrats. The party gained seats in the House of Representatives in 1998 and in 2006 a war-weary nation delivered the House and Senate to Democrats. In each of these years, national trends influenced Maryland's elections.

If 2010 is like 1994 and 2002, Ehrlich has a chance at reclaiming his old job. If it's like 1998 and 2006, Ehrlich should let state Republicans designate some other sacrificial lamb.

A GOP year?

Next year is shaping up to be a 1994/2002 election. Gallup reports Republicans lead Democrats 48 percent to 44 percent on the generic congressional ballot. Republicans last held an advantage in 1994 and 2002. Independent voters prefer Republicans 52 percent to 30 percent.

The 1994 Republican wave was presaged by gubernatorial victories in Virginia and New Jersey in 1993. Republicans swept both states in 2009. The Cook Political Report indicates that 38 of 50 competitive House seats in 2010 are Democratic.

Using current voter registration data, I modeled the potential outcome of an Ehrlich/O'Malley rematch based on prior turnout and partisan performance for each party and found that O'Malley would narrowly win re-election even if the 2010 gubernatorial election follows the patterns of 1994 or 2002. The result is a simple reflection of the increased registration advantaged enjoyed by the Democrats. Even in a strong Republican year, Ehrlich would face an uphill struggle.

Still, if Ehrlich could repeat his strong performance and hold O'Malley to the Democrats' depressed performance of 1994, he could win. A recent Clarus Poll shows that scenario is possible. O'Malley led Ehrlich 47 percent to 40 percent, but he polled below 50 percent and only 39 percent of respondents wanted to see him re-elected. His approval rating was 48 percent and those ratings often forecast an incumbent's final vote total.

The Democrats' registration advantage may be overstated. Many voters registered Democrat to participate in the historic 2008 primary. Similar gains in Virginia and New Jersey in 2008 failed to materialize in 2009. Based on past trends in party registration, the Democrats' advantage may be overstated by nearly 200,000 voters.

Should Ehrlich run?

Ehrlich will likely never have a better opportunity. A Republican presidential victory in 2012 would make 2014 a less hospitable year. An Obama re-election may make 2014 a good year for the GOP, but after eight years out of public office, would Ehrlich still be viable? Ehrlich could consider a run for the Senate, but Sen. Barbara Mikulski seems invincible. That would leave 2012 and Sen. Ben Cardin's seat, but Obama carried Maryland 62 percent to 37 percent in 2008 and would share the ballot in 2012; I would expect down-ballot coattails. For all the challenges, 2010 presents Ehrlich with his best chance for reclaiming the governorship. That's the reality that he must grapple with.

Todd Eberly is an assistant professor of political science at St. Mary's College of Maryland.

Blair Lee's column will return next week.